1. Technical Field
The present invention relates to the sampling of gases and, more particularly, to a device and method for measuring the level of elemental sulfur present in a gas in a gas line.
2. Description of the Related Art
Knowing of the presence of elemental sulfur in gas in a gas line is of high importance to engineers working with gas processing systems. Elemental sulfur vapor in a gas line can undergo condensation or deposition, either within the gas line or further downstream, and cause numerous problems, including unsafe, unreliable operations and increased maintenance costs. Condensed or deposed sulfur can cause corrosion acceleration and/or blockage by sulfur precipitates in process unit operations, which can interrupt the normal operation of the gas processing plant and, in some cases, require plant shutdown and diversion of the gas to another plant. These types of interruptions represent a safety hazard and often lead to environmental concerns. For example, if the blockage materials must be diverted to a burning pit, undesirable chemical fumes may be produced. In addition, the interruptions can be costly and often require manpower to locate and clear up blockage materials. Thus, it is desired to have the ability to measure the amount of elemental sulfur in gas in gas lines to avoid these and other problems.
Various devices and methods for measuring the amount of elemental sulfur present in gas in a gas line have been proposed; however, they have been ineffective and suffer from many disadvantages. For example, these devices and methods have not been able to provide accurate measurements, in part because elemental sulfur is usually present in extremely small quantities, i.e., parts per million or parts per billion. Also, available analytical techniques and instruments only measure the total sulfur present in the gas, and do not distinguish between free elemental sulfur and sulfur in other sulfur-containing chemicals, particularly in sour gas systems. Further, these previously proposed devices and methods are not particularly suitable for measuring elemental sulfur levels in gases in pressurized gas lines. In that regard, the use of sampling cylinders has been previously proposed. However, because elemental sulfur vapor condenses at temperatures below 52 degrees Celsius, when taking gas samples from pressurized gas pipelines for laboratory analysis, the sulfur condenses on the internal wall of the sampling cylinder, thus making sampling cylinders ineffective. Laboratory simulations have been performed and proposed. These simulations, however, have been performed in highly controlled environments and involve the evaporation of sulfur powder, and do not appear to be practical or accurate for real world applications involving, for example, pressurized gas streams.
Accordingly, prior to the development of the present invention, there has been no single device and method for measuring elemental sulfur in gas in gas lines which: provides an accurate measurement of elemental sulfur, can distinguish between free elemental sulfur and sulfur in other sulfur-containing chemicals, and is practical and effective when utilized in process plant applications, particularly in pressurized gas lines. Therefore, the art has sought a device and method for measuring elemental sulfur in gas in gas lines which: provides an accurate measurement of elemental sulfur, can distinguish between free elemental sulfur and sulfur in other sulfur-containing chemicals, and is practical and effective when utilized in process plant applications, particularly pressurized gas lines.